An aircraft landing gear assembly is generally movable between a deployed condition, for take off and landing, and a stowed condition for flight.
An actuator may be provided for moving the landing gear assembly between the deployed and stowed conditions. This type of actuator is known in the art as a “retraction actuator”. A retraction actuator may have one end coupled to the airframe and another end coupled to the main strut such that extension and retraction of the actuator results in movement of the main strut between deployed and stowed conditions.
One or more stay assemblies may be provided to support the orientation of the main strut when the landing gear assembly is in the deployed condition. A stay assembly generally includes a stay and a lock link arranged to maintain the stay in a condition which corresponds to the landing gear assembly being in the deployed condition. The lock link must be ‘broken’ to enable the stay to be folded, permitting the main strut to be moved by the retraction actuator towards the stowed condition.
It is common for landing gear assemblies to be arranged to move towards the deployed condition in the event of a failure of the retraction actuator. Initially the assembly will move by way of gravity and in doing so the landing gear assembly forces the stay to move towards the condition which corresponds to the landing gear assembly being in the deployed condition. One or more ‘down locking’ springs may be provided to assist in moving landing gear assembly to the deployed condition and locking it in that state by ‘making’ the lock link. Landing gear assemblies for larger aircraft may be provided with a pair of down locking springs on each stay assembly.
In order to meet down locking requirements on larger aircraft, such as those requiring four or six wheeled bogie beams on the main landing gear assembly (MLG), large down locking springs are required. In some cases this is due to the characteristics of a ‘four point’ attachment dual stay MLG, where the dual stays provide attachment points on the forward and aft sides of the landing gear to transfer drag and side loads into the airframe. Springs with a large wire diameter can however be undesirably heavy and can be difficult to manufacture.